j-d wrote:
They come with four aluminum angle brackets. The short edge of the brackets fasten to the vertical part of your roof vent flange. The long edge hugs the roof surface and the vent cover fastens there.
So installation is drilling four small holes in each flange then assembling the brackets and dropping the cover down onto the brackets and applying a nut.
NO penetration of the roof fiberglass or rubber sheet.
Here is a You Tube video that shows what j-d is talking about, this may help in your install.
YOU TUBE VIDEOGood Luck